Gonzales was summoned before a grand jury that has been meeting for six months, taking testimony in an inquiry led by special prosecutor Patrick J. Fitzgerald.

White House press secretary Scott McClellan confirmed Gonzales's appearance before the panel but said he had no information about why Gonzales was called or what he was asked. "The judge was pleased to do his part to cooperate," McClellan said about the appearance.

Gonzales has coordinated the White House's response to subpoenas and document requests from Fitzgerald's office. McClellan said he did not know whether Gonzales was summoned to answer questions about the custody and production of documents.

Plame is married to former ambassador Joseph C. Wilson IV, a critic of the Bush administration who contends that his wife's identity as an undercover CIA officer was leaked as retaliation for his criticism. Wilson was asked by the CIA in 2002 to investigate claims that Iraq had sought to buy "yellowcake" uranium in the African country of Niger, and last year he said publicly that he found no evidence to support the contentions.

The prosecutor has sought records -- including phone records, calendars and e-mails -- that would reflect any contact between White House aides and reporters concerning Wilson, his trip to Africa or Plame.

Vice President Cheney was recently interviewed by Fitzgerald's staff, and President Bush has consulted with a private lawyer in the event he is questioned about the Plame disclosure.

In recent weeks, Fitzgerald has subpoenaed journalist Tim Russert of NBC and Time reporter Matt Cooper as part of the investigation. News organizations have gone to court seeking to quash the subpoenas.

McClellan said he did not know of any other White House aides who were called before the panel in recent weeks.